From pretty butterflies to pesky mosquitoes — insects are among the most diverse and dominant groups on earth. Nearly 1 million species are known to exist and there are likely many more to be discovered. According to a UN biodiversity study, up to 40% of insects species are threatened with extinction in some parts of the world. Many people do not realize that their loss would be keenly felt.

Crops, such as wheat, are wind pollinated, but many other food crops depend on insects for pollination. Their disappearance would come at great cost to farmers. Some $235 billion of yearly global food production relies on pollinators. In some farms in China, workers are hand-pollinating apple and pear trees because of the lack of bees. Such labor-intensive work pushes up food prices.

Pollinator disappearance also means we'd lack much of the fruit and vegetables we eat — and we wouldn't be enjoying beloved treats like chocolate and coffee. Apart from food, pollinators also contribute to the fibers, such as cotton, from which we make our clothes, as well as to plants on which certain medicines are based.

Many insects, like the dung beetle pictured here, decompose dead plant matter, carrion and feces that would otherwise be left to decay in our environment. Basically, the world would be a smellier and less hygienic place without them.

Insects are the main source of food for many other animals, including amphibians, reptiles, certain mammals, and birds. And as insects disappear, there could be declines in the species that feed on them too. Ornithologists believe sharp declines in bird species in the UK, for instance, are at least partly linked to a drop in insect numbers.

Climate change is also affecting insects that are slow to adapt. Bumblebees for instance are suited to cool and wet climates and may find it difficult in warmer weather. But insects that are pests are already spreading to new habitats. The European corn borer (pictured), which can destroy corn harvests, is among them. That means farmers use more pesticides that kill pollinating insects.

Intensive farming is one of the major factors behind insect declines in Europe. Fertilizers, pesticides and insecticides are all driving the decline, as are monocultures — the practise of growing of a single crop or plant. That takes refuge and habitat, like diverse flowering meadows, away from insects.

Experts say a more insect-friendly farming policy that relies less on pesticides and monocultures would boost their numbers. But planting blooming flowers in gardens and urban areas would also provide food and habitat for bumblebees and butterflies. Another option is building more "insect hotels," (pictured) for solitary critters, like leafcutter bees, which like to nest in tunnels.

What can be seen here is probably the first thing that comes to mind when we think of bees — honey! Here the sugar crystals have been magnified 100 times with the help of a polarized light. For one jar of honey, bees have to visit between 450,000 and 3 million flowers.

Many people don't realise that honey is just a fraction of the food bees help produce. The above photo shows what a supermarket would look like if bees didn't exist. That amounted to 60% of the items on the shelves. Various spices, marinades, dairy products, and even scented toilet paper, are all possible in part thanks to the efforts of bees.

Not all bees are the same. A wild bee, for example, does not produce honey but it's a key pollinator. It's also particularly at risk of extinction. Bumble bees are also among the wild bee species. Honey bees, on the other hand, have less to worry about because they are domesticated and highly managed for agricultural use, with their hives kept by humans.

Of course there are other pollinators besides bees — butterflies, flies and birds, for example. But about a third of our fruit and vegetables rely on pollination by bees. These include apples, pears, strawberries and cucumbers. And we would all be reluctant to do without them, wouldn't we?

How is it possible for our chocolate, sweets, fruit and vegetables to look so beautiful? Bees, of course. Or, more specifically, E901 — beeswax. It gives chocolate its beautiful shine and makes vegetables look waxed and appetizing, as well as ensuring they retain moisture and stay fresh. It's also used as a glazing and separating agent for candy so that gummy bears don't all stick together.

And about chocolate — without bees, there wouldn't be much of it. Bees are responsible for pollinating a lot of cocoa. If it came to it, the only option could be to pollinate by hand, which would be extremely labor-intensive and much less efficient. The same goes for nuts, by the way.

It's not just humans that like coffee. Bees do too, as an experiment with coffee-free and coffee-infused sugar water has shown. At the same time, bees do the work to pollinate our coffee beans, to maintain our (hopefully) never ending supply of caffeine.

By now it's clear how much we benefit from the hard work of bees and how different our lives would be without them. But we shouldn't just pay tribute to them on World Bee Day. Appreciating bees means protecting them. The most restrained use of pesticides helps. Insect boxes also provide safety, nesting and hiberation. And flowers in a balcony box or fruit trees outside are a safe source of food.